A double-worm or double-screw extruders has a housing with at least two compartments extending over its length and a drive at an end of the housing for rotating the screws or worms in the same or opposite senses. The screws are rotatable in the respective chambers of the extruder housing and have their flights intercalated so that they subject a synthetic-resin mass to plastification and liquefication. The extruder also pressurizes the thermoplastified mass so as to force the synthetic resin material through an extrusion die or into a mold.
The drive housing has a mechanism for rotating the worms or screws and the principles described are applicable not only to two-worm extruders but also extruders having more than two worms. It is common to provide so-called double-worm or double-screw extruders with a drive motor which is coupled to the two worms or screws. For example, the extruder screws can be connected by means of a transmission with the drive motor. depending on the type of drive or transmission used, the double-screw extruder can be relatively bulky. In addition, the transmission or drive may be subject to failure and the maintenance thereof can be comparatively expensive.
In one system, each of the screws or worms with a double-screw extruder can be separately driven by a respective drive motor and corresponding transmission. To achieve synchronism between the two extruder screws, the two drives can be coupled with one another. This arrangement also is quite voluminous and there always may be problems with the reliability of the synchronism system. In addition, such double-screw extruders are comparatively expensive.
These earlier systems lack a simple, space-saving drive system for a multiscrew extruder with reliable synchronism of the extruder screws.